Experimental study and numerical analysis of radiative losses of single-channel solar chimney

Abstract

Solar chimneys provide natural ventilation for buildings, reducing the energy consumption of mechanical systems. Therefore, analyzing energy losses through solar chimney components and inlet/outlet of air channel is critical to develop a suitable design for this passive ventilation system. In this study, the performance and energy losses analysis of a single-channel solar chimney (SC-SOCH) is described; a parametric study under laboratory conditions was conducted regarding the air gap (0.10, 0.15, and 0.20 m) and heat flux of absorber plate (100, 200, 300, 400, and 500 Wm−2). The energy losses were analyzed with temperature sensors, heat flow transducers, and a net radiation transfer model. The parametric study results showed that between 10% and 15% of the total energy supplied to the absorber plate was dissipated to the laboratory environment through the glass cover. Furthermore, combining the different thermal insulation layers on the backside of the absorber plate and sidewalls of the air channel permitted only energy losses below 8% of the total energy supplied. The highest energy losses occurred due to radiative exchange; the radiative losses through the inlet and outlet of the air channel were between 9.38% and 25.78% of the total energy supplied. However, the radiative energy loss rate decreased as airflow increased; the volumetric flow rate was from 34.11 to 94.92 m3h−1, which was enough to satisfy the requirements of total ventilation rate for spaces of 9, 18, and 36 m2 according to ASHRAE 62.2–2019. Therefore, solar chimney designs must be optimized to minimize energy losses and increase airflow for natural ventilation.

Integrating physical experiments with computational fluid dynamics to transform mosque minarets into efficient solar chimneys

“…4 . Cairo, specifically, is situated in a hot, dry zone 9 . The city has a significant number of mosques, earning it the epithet 'the city of the thousand minarets’ 39 .…”

“…Studies suggest that minaret design may have been inspired by contemporary fashion. This is particularly evident in the resemblance between headscarves and the tops of minarets, symbolizing the minaret as a distinctive emblem of the Islamic state across different periods 9 .…”

“…Studies have found that an integrated system with solar chimneys can reduce energy consumption by up to 50% 27 . Additionally, they can be used as part of a hybrid ventilation system, combining natural and mechanical ventilation for optimal performance 9 . Solar chimneys have also been found to be effective at reducing indoor temperatures during hot summer months 28 .…”

Annual Evaluation of Natural Ventilation Induction in Solar Chimneys under Tropical, Dry, and Temperate Climates of Mexico: A Case Study

“…The solution methodology and GEB models were validated using experimental data of the SC-SoCh prototype reported in [31]. The SC-SoCh prototype was evaluated under controlled conditions.…”

“…The proposed models consider additional climatic variables compared to those reported in the literature, e.g., solar radiation, ambient temperature, wind speed, atmospheric pressure, and relative humidity changes, for accurate air density calculation, which is crucial for calculating the induced ventilation by SCs. The GEB experimental evaluation was validated through experimental data from a SC-SoCh prototype [31]. The validated models permit an annual evaluation and comparison between SC-SoCh and TC-SoCh performance under Mexico's extensive and detailed climatic conditions for a year to find a passive system to induce natural ventilation for buildings.…”